I have MTHFR & PAI-1. I took the liberty of taking my blood results to a hemotolgist. I suggest the same for you & they can tell you what is best for future pregancy. I am sorry this has happend to you.
I also have Factor V Leiden (heterozygote), and I had two miscarriages before I had a successful IVF. The first miscarriage, I wasn't on any blood thinners and went to 8 weeks, when the embryo stopped developing and I had to have a D&C. The second time I got pregnant, I was already on baby aspirin and I was suppose to start Lovenox shots once a heartbeat was detected. Well I started spotting the day of my 6 week appointment, and was cramping by the time I got to the doctor. They did see a heartbeat, and I picked up the lovenox on the way home, but never got to start it, as I miscarried naturally that night. After that I just wasn't getting pregnant again, so after a year and a half with charting, timed intercourse, and then fertility medication and IUIs, we decided not to waste any more time, so we ended up doing IVF last Spring...and this time, since everything was so well controlled, I was on blood thinners from the very beginning...and it worked! I had a healthy baby girl right before Christmas. I was super nervous the entire time, though.
Since Lovenox stays in your system a lot longer than heparin, I was switched to heparin the last month or so (they don't want blood thinners in your system when you deliver, since there are additional bleeding risks involved), and I was on 5000 IU twice a day. I'm 1.68 and about 55 kg.
I hope things work out for you and that you have a successful, full-term pregnancy next time. Best of luck with everything and let me know if you have any other questions.